Development study of Diffusive Gradient in Thin Film (DGT) method with binding agent Fe−Ca complex for phosphate measurement

The inclusion of phosphorus as a phosphate compound into the aquatic system causes environmental problems, for which monitoring is required in particular on waste treatment. The Diffusive Gradient in Thin Film (DGT) technique with ferrihydrite as binding gel is commonly used for in situ phosphate measurement. Studies on Fe−Mn binary oxide adsorbent have been performed but are only able to absorb phosphate optimally at pH 3−5. In addition to ferric salts, calcium salt is an effective chemical reagent in absorbing phosphate. This research develops new technology by combining both reagent into Fe−Ca complex. The result of this study show that Fe−Ca complex has an antagonistic effect in absorbing phosphate at molar ratio of Fe−Ca 1: 1.5 to 1: 5 and has a synergistic effect when the molar ratio of Fe is increased from 1: 1 to 5: 1. The Optimum absorption occurs in the molar ratio of Fe−Ca complex 3: 1. The measurement of phosphate by spectrophotometric method of molybdenum blue known that Fe−Ca complex has wide working area that is in pH range 2.0−10.0 with optimum contact time 24 hours. Based on the results obtained Fe−Ca complex can be one alternative binding gel on phosphate measurement with DGT technique. (paper)